1. Field of the Invention
The present invention relates to a new wedge-base bulb in which light emitted to the outside is colored by a colored coating on the glass bulb, as well as a method for applying the colored coating to the glass bulb.
2. Background Art
There is a bulb called a wedge-base bulb in which a filament and a lead supporting the filament are disposed in a glass bulb, and a portion of the lead is led out to the outside from a base portion formed at one end portion of the glass bulb, so that the led-out portion of the lead forms a current-conducting terminal.
Such a wedge-base bulb is mainly used as a light source of an automotive identification lamp, such as a turn signal lamp, a brake lamp, etc. Although the light emitted from a wedge-base bulb is nearly colorless, orange (amber) light is required for the turn signal lamp, and red light is required for the brake lamp.
Therefore, conventionally, a front lens covering the front side of the identification lamp is formed of a transparent member which is colored orange or red. Alternatively, a so-called cap, which is transparent and colored orange or red, is put on the wedge-base bulb to cover its circumference, so that light having a desired color is emitted to the outside.
In the case of using a cap for obtaining light having a desired color, the cap is required in addition to the regular parts that constitute the automotive identification lamp. Accordingly, this increases the number of parts and therefore the manufacturing cost of the automotive identification lamp.
On the other hand, a front lens for covering the front side of the identification lamp is formed of a transparent. member and colored orange or red, as in the case of a so-called rear combination lamp typically used at a rear portion of a car. In a rear combination lamp, a turn signal lamp, a brake lamp, a tail lamp and a back lamp are provided integrally. The front lens covering the entire front side of the rear combination lamp must be a multi-color member colored in orange, red or other colors. Accordingly, this increases the manufacturing cost, and otherwise limits the design of the rear combination lamp and the vehicle.
Taking the foregoing problems into consideration, it is an object of the present invention to provide a wedge-base bulb in which it is possible to eliminate the need for a cap for coloring the light emitted from the wedge-base bulb, or a colored front lens of an automotive identification lamp.
In order to solve the foregoing problems, in a wedge-base bulb according to the present invention, a colored coating is formed on the surface of the glass bulb. When the colored coating is formed, excess colored coating material drips away from the base portion and terminals due to the presence of grooves and/or ribs between the glass bulb and a base portion of the wedge-base bulb.
Consequently, it is not necessary to use a cap or a colored front lens for coloring the light emitted from the wedge-base bulb in a desired color.